1. Technological Field
The present invention relates to a small timepiece gear and a method for manufacturing the timepiece gear.
2. Background Technology
The device disclosed in Patent Document 1 is a known example of an electronically controlled mechanical timepiece provided with a train wheel mechanism.
The train wheel mechanism of Patent Document 1 has a barrel wheel for housing a mainspring in order to store mechanical energy, and the gears of second (central) to sixth wheels and pinions that serially mesh in order to transmit the mechanical energy of the mainspring to a rotor of a power generator. The rotation of the barrel wheel is transmitted to a center wheel and pinion, the rotation of the center wheel and pinion is increased and transmitted to the third wheel and pinion. The rotation of the third wheel and pinion is further increased and transmitted from the fourth wheel and pinion to the rotor via the sixth wheel and pinion.
The second (central) to sixth wheels and pinions are composed of components having a pinion and shaft member that are rotating shafts, being mutually coaxially formed, and a tooth part having a larger diameter than the pinion and being integrally formed on the external periphery of the shaft member. For example, the pinion and shaft member are formed by grinding using a lathe or the like, and the tooth part is formed in the shape of a disc by grinding or by using a punch press or the like while a securing hole is provided in a center position of a plate-shaped member. Each wheel is formed by cutting out the pinion and the tooth of the tooth part by gear milling and thereafter passing the shaft member through the securing hole and securing the shaft member.
In the train wheel mechanism, the greatest meshing stress, in comparison with the portion that meshes with another wheel, acts on the center tooth part of the center wheel and pinion for increasing and transmitting the rotation of the barrel wheel and on the portion that meshes with the third pinion of the third wheel and pinion.
Accordingly, in Patent Document 1, the center wheel and pinion and the third wheel and pinion are formed using a crystalline metal as a material having high-hardness properties (anti-abrasion properties), or the high-hardness central wheel and pinion and third wheel and pinion are formed by subjecting the matrix material of the crystalline metal to a hardening treatment in order to increase the durability and reliability of a timepiece.
[Patent Document 1] Japanese Laid-open Patent Application No. 2002-323114 (FIGS. 1 to 4)